Solids discharge centrifuge



p 8,1964 K. G. REED 3,148,145

SOLIDS DISCHARGE CENTRIFUGE Filed March 25, 1963 INVENTOR.

KARL G. RE D M ATTORNEY United States Patent 3,148,145 SOLIDS DISSHARGECENTRIFUGE Karl G. Reed, Wayne, Pa., assignor to Pennsalt ChemicaisCorporation, a corporation of Pennsylvania Filed Mar. 25, 1963, Ser. No.267,633 3 Claims. (Cl. 233-7) This invention relates to a centrifuge.More specifically this invention relates to a centrifuge containing anaxially disposed conveyor element rotating at a speed different fromthat of the centrifuge bowl and serving to move solids toward the solidsdischarge port.

In the centrifugal separation of solids from a liquid it has been quitecommon to provide a centrifuge bowl with a solids discharge port inwardfrom the liquid discharge port and an axially disposed conveyor elementusually in the form of a helical edge which rotates at a speed differentfrom that of the centrifuge bowl to move the solids inward out of theliquid in the bowl to the solids discharge port for discharge. As thesolids are moved inward out of the liquid and toward the discharge theydrain on an inwardly tapered wall portion and become comparatively dryas they reach the discharge port. An example of a machine operating inthis manner is disclosed in the U.S. Patent 2,703,676, which issuedMarch 8, 1955, on an application filed by Fred P. Gooch.

In moving the solids inward out of the liquid and toward the solidsdischarge port a thrust caused by the resistance to movement of thesolids urges the conveyor in a direction away from the solids dischargeport. In the prior art machines this thrust has conventionally beenborne by a thrust bearing disposed between the conveyor and the end wallof the centrifuge opposite the solids discharge port. This end wall, orfront hub, has been, especially in large machines, of necessity, massiveto withstand the lateral urging on the periphery of the hub by the bowlshell without bending. Further, extremely rugged connecting means, e.g.bowl shell flanges and many flange bolts, have been required to hold thehub and peripheral wall together. The rugged and massive nature of theseparts has been dictated not only by the thrust forces but also by theinternal liquid pressure present in the bowl at the juncture of the huband bowl shell. This heavy structure has increased the power required toaccelerate the centrifuge, has increased the expense of construction andhas complicated balancing procedures.

In addition to the disadvantages of high strength structures, thelocation of the thrust bearing elements within the centrifuge has madethem inaccessible for easy inspection, repair and replacement. Forinstance, to merely inspect the thrust bearing in the prior art machinesit has been necessary to remove the rotor from its frame, and remove thefront hub with the gear box and shaft from the bowl shell. Suchprocedure has not only consumed excessive time of the repairman andoperator, but, more importantly, has had a major effect on the amount oflost production time.

It is, therefore, an object of the present invention to provide acentrifuge of the type described in which the reaction forces generatedby the scrolling of solids toward the solids discharge port is in acompressive form borne at the juncture of the bowl shell and the rearhub, or end wall of the machine adjacent the solids discharge port.Since the diameters of the parts at the solids discharge portion of thebowl are significantly less than at the front hub where the forces havepreviously been borne, the connecting portions, that is the flanges andflange bolts, need not be significantly strengthened. This is especiallytrue in comparison with the juncture of the front hub and bowl shell ofthe old design, since under the present invention the juncture of thebowl shell and rear hub is inward of the liquid in the bowl and is notsubject to liquid pressures.

It is a further object of the invention to provide in the centrifuge ofthe type described for the easy accessibility of the thrust hearing fromthe outside of the centrifuge.

Other features and objects of the invention will be apparent from thefollowing description of an apparatus embodying the invention and shownin the accompanying drawings wherein the figure is a broken sectionalview, partly in elevation, of an apparatus embodying the invention, theliquid level and separated solids being shown in phantom.

Referring more specifically to the drawings, a centrifuge embodying theinvention is designated 10 in the figure. It comprises a frame 12supporting a pair of pillow block bearings 14. Mounted for rotation inthe bearings is the rotor or centrifuge bowl 16 comprising a front hub18 secured at a peripheral flange to the bowl shell 20. At the oppositeend the rotor comprises the rear hub or wall 22. A tapered wall portion20a comprises part of the bowl shell and is secured at its end to therear hub.

A liquid discharge port 26 is provided in a plate dam 28 secured in thefront hub 18. A solids discharge port 30 having the outermost edge ofits inner lip disposed inwardly of the outermost margin of the liquiddischarge port 26 is disposed adjacent the rear hub 22 in the taperedwall portion 20a.

Rotatably mounted on bearings 32 within the rotor 16 is the conveyor 34.The body of the conveyor 34 is formed with outwardly extending flightportions 36, the edges of which are disposed closely adjacent the insidesurface of the rotor shell. Threadedly secured to the rightward end ofthe conveyor 34 as shown in the figure is the tension element 38extending in a central hollow portion of the rotor within the rightwardbearing 14. As shown, on the side opposite the rightward bearing 14 fromthe centrifuge bowl the rotor is provided with a pulley means 40 bywhich the rotor may be driven. Internally the pulley means 40 is formedwith a radial shoulder 42 and the tension element 38 is formed with anenlargement presenting a radial shoulder 44 opposing shoulder 42.Intermediate the shoulders 42 and 44 is disposed in compression thethrust bearing means 46 comprising in the embodiment shown a rollerbearing. The seal 40a closes the compartment defined by the pulleymeans.

As in prior art devices, such as the device of the above-mentionedpatent, the rotor shaft extending through the leftward bearing 14 issecured to an appropriate gear box (not shown) containing a suitablegear train by which rotary motion is transmitted at the desireddifferential to the conveyor shaft 48 which is splined at 50 to drivethe conveyor.

The feed tube 52 extends through the tension element 38 and is adaptedto deliver feed mixture against the accelerator plate 53 and through thefeed port 54 in the conveyor body. At its rightward end the feed tube 52is supported by a bracket 56. A cover 58 is secured to the frame 12 andcollects the separated discharges as is conventional.

In operation with the rotor 16 rotating at an appropriate speed, forinstance 4000 r.p.m., and the conveyor driven through the gear box at asuitable differential, the liquid solids mixture is delivered to therotor through the feed tube 52 and the feed port 54. Under the infiuenceof centrifugal force the heavier solids settle in the liquid to form alayer against the bowl shell 20. The clarified liquid passes out theliquid discharge port 26 and thereby establishes the level of liquid inthe rotor at the level of the port. The solids are moved by the edges offlights in a rightward direction inward out of the liquid to the solidsdischarge port 36). In so moving to and out of the port the solidsbecome dry as they drain on the tapered wall portion 29a. By being thusconcentrated and dried the solids increase in their resistance to inwardmovement by the conveyor flights and as a reac tion to the force appliedagainst them the solids urge the entire conveyor in a leftward directionas shown in the figure. The leftward urging creates a tension in theelement 38 and a compressive force on the bearing means 46. Thecompression force is carried through the rotor shaft within therightward bearing 14 and through the juncture of the tapered wallportion a and the rear hub 22.

Unlike the prior art forms in which the thrust of the conveyor actedagainst the front hub and required massive flanges and many connectorsbetween the front hub and the bowl shell, under the present arrangementthe compressive force is easily absorbed at the juncture of the taperedwall portion 20a and the rear hub 22. This is especially true sinceunlike the prior forms, at this juncture there is no liquid pressure.Hence the power required to accelerate the present machine and theamount of metal required to build it and hence the expense aresignificantly less than in prior comparable structures. Further, byhaving the bearing means 46 outside of the centrifuge it is readilyaccessible to inspection, repair or replacement. As will be understood,to inspect the bearing means 46 it is merely necessary to remove thefeed tube 52, the tension element 38 and the pulley seal 46a.

Variations of the apparatus shown are possible within the scope of theappended claims. Hence while I have explained my invention with the aidof a particular embodiment thereof, it is to be understood that I do notwish to be limited to the specific structural details illustrated anddescribed from which departure can be made without departing from thespirit and scope of the invention as defined by the following claims.

I claim:

1. A centrifuge comprising:

(a) a rotor mounted to rotate about a horizontal axis and having a pairof end walls and an imperforate peripheral shell with a portion taperinginwardly toward one end, the shell being secured between the end walls,the rotor having a solids discharge port at the said end, the end wallat the said end having a central opening, the other end of the rotorhaving a liquid discharge port inward from the shell but at a radiusgreater than the solids discharge port, the said end wall and the shellmeeting at an inner juncture, the inner juncture being radially inwardfrom the liquid discharge port, the other end wall and the shell meetingat an outer juncture, the outer juncture being radially outward from theliquid discharge port,

(7)) a conveyor rotatably supported within the rotor, the conveyorhaving a body portion and a helical edge portion supported by the bodyportion, the helical edge portion being closely adjacent the shell andadapted in rotating to move solids toward the solids discharge port,

(c) a tension element removably secured to the conveyor and extendingthrough the central opening in the said one end wall,

(d) means to supply feed mixture to the interior of the rotor,

(e) means to drive the rotor and the conveyor at different speedsincluding a drive shaft on the rotor and surrounding the tension elementand presenting a shoulder facing away from the rotor,

(f) enlarged means on the tension element on the opposite side of theshoulder from the rotor, the shoulder and the enlarged means beingaxially spaced and the enlarged means presenting a second shouldergenerally facing the first-mentioned shoulder, and

(g) thrust bearing means having freely rolling elements and disposed inthe space and held in axial compression between the shoulders,

whereby the forces developed between the conveyor and the rotor as theconveyor moves the solids toward the solids discharge port appear as acompressive force acting at the inner juncture instead of as a tensionforce at the outer juncture.

2. A centrifuge as described in claim 1 wherein the conveyor bodyportion has an axial threaded opening in its end adjacent the said endof the rotor, the tension element is tubular and threaded on one end andhas an enlarged head on the other, the threaded end being threadedlyreceived into the last-mentioned opening and the head comprising theenlarged means.

3. A centrifuge comprising:

(a) a rotor mounted to rotate about a horizontal axis and having a pairof end walls and an imperforate peripheral shell with a portion taperinginwardly toward one end, the shell being secured between the end walls,the rotor having a solids discharge port at the said end, the end wallat the said end having a central opening, the other end of the rotorhaving a liquid discharge port inward from the shell but at a radiusgreater than the solids discharge port, the said end wall and the shellmeeting at an inner juncture, the inner juncture being radially inwardfrom the liquid discharge port, the other end wall and the shell meetingat an outer juncture, the outer juncture being radially outward from theliquid discharge port,

(b) a conveyor rotatably supported within the rotor, the conveyor havinga body portion and a helical edge portion supported by the body portion,the helical edge portion being closely adjacent the shell and adapted inrotating to move solids toward the solids discharge port,

(c) means to supply feed mixture to the interior of the rotor,

(d) means to drive the rotor and the conveyor at different speedsincluding a tubular drive shaft on the rotor and extending axially outfrom the said end about the central opening, and presenting a shoulderfacing away from the rotor,

(e) thrust bearing means having freely rolling elements and having aninner face abutting about said shoulder and an outer face directed awayfrom the rotor,

(f) force-conducting means extending through the opening in the said endwall and through the tubular drive shaft and including a threaded,readily disassemblable joint and connecting the conveyor and the outerface of the thrust bearing means so that axial thrust of the conveyor ina direction toward the said other end wall is borne by the thrustbearing means,

whereby the forces developed between the conveyor and the rotor as theconveyor moves the solids toward the solids discharge port appear as acompressive force acting at the inner juncture instead of as a tensionforce at the outer juncture.

(References on following page) UNITED STATES PATENTS Whitely et a1. Jan.22, 1902 Rigler Apr. 18, 1933 Howe Feb. 27, 1945 Messinger Nov. 4, 1947Hertrich Feb. 22, 1949 Milliken et a1. June 10, 1952 Ritsch Oct. 21,1952 6 Kuster et a1. Aug. 25, 1953 Crossley Aug. 3, 1954 Gooch Mar. 8,1955 Cook et a1. Oct. 14, 1958 Harlow Jan. 6, 1959 Gooch Oct. 30, 1962FOREIGN PATENTS Germany Sept. 27, 1915 Disclaimer 3,148,145-5'1172 G.Reed, Wayne, Pa. SOLIDS DISCHARGE CENTRL FUGE. Patent dated Sept. 8,1964. Disclaimer filed Mar. 5, 1965, by the assignee, PennsaltUhemica-Zs Gowpomtz'on. Hereby enters this disclaimer to claim 3 of saidpatient.

[Ofiieial Gazette June 15,1965] Disclaimer 3,1&8,145.Karl G. Reed,Wayne, Pa. SOLIDS DISCHARGE 'CENTRI- FUGE. Patent dated Sept. 8, 1964:.Disclaimer filed June 9, 1965, by the assignee, Pennsalt OhemioalsCorpomtion. Hereby enters this disclaimer to claim 1 of said patent.

[Ofice'al Gazette September 14, 1965.]

1. A CENTRIFUGE COMPRISING: (A) A ROTOR MOUNTED TO ROTATE ABOUT AHORIZONTAL AXIS AND HAVING A PAIR OF END WALLS AND AN IMPERFORATEPERIPHERAL SHELL WITH A PORTION TAPERING INWARDLY TOWARD ONE END, THESHELL BEING SECURED BETWEEN THE END WALLS, THE ROTOR HAVING A SOLIDSDISCHARGE PORT AT THE SAID END, THE END WALL AT THE SAID END HAVING ACENTRAL OPENING, THE OTHER END, OF THE ROTOR HAVING A LIQUID DISCHARGEPORT INWARD FROM THE SHELL BUT AT A RADIUS GREATER THAN THE SOLIDSDISCHARGE PORT, THE SAID END WALL AND THE SHELL MEETING AT AN INNERJUNCTURE, THE INNER JUNCTION BEING RADIALLY INWARD FROM THE LIQUIDDISCHARGE PORT, THE OTHER END WALL AND THE SHELL MEETING AT AN OUTERJUNCTION, THE OUTER JUNCTURE BEING RADIALLY OUTWARD FROM THE LIQUIDDISCHARGE PORT, (B) A CONVEYOR ROTATABLY SUPPORTED WITHIN THE ROTOR, THECONVEYOR HAVING A BODY PORTION AND A HELICAL EDGE PORTION SUPPORTED BYTHE BODY PORTION, THE HELICAL EDGE PORTION BEING CLOSELY ADJACENT THESHELL AND ADAPTED IN ROTATING TO MOVE SOLIDS TOWARD THE SOLIDS DISCHARGEPORT, (C) A TENSION ELEMENT REMOVABLY SECURED TO THE CONVEYOR ANDEXTENDING THROUGH THE CENTRAL OPENING IN THE SAID ONE END WALL, (D)MEANS TO SUPPLY FEED MIXTURE TO THE INTERIOR OF THE ROTOR, (E) MEANS TOPROVIDE THE ROTOR AND THE CONVEYOR AT DIFFERENT SPEEDS INCLUDING A DRIVESHAFT ON THE ROTOR AND SURROUNDING THE TENSION ELEMENT AND PRESENTING ASHOULDER FACING AWAY FROM THE ROTOR, (F) ENLARGED MEANS ON THE TENSIONELEMENT ON THE OPPOSITE SIDE OF THE SHOULDER FROM THE ROTOR, THESHOULDER AND THE ENLARGED MEANS BEING AXIALLY SPACED AND THE ENLARGEDMEANS PRESENTING A SECOND SHOULDER GENERALLY FACING THE FIRST-MENTIONEDSHOULDER, AND (G) THRUST BEARING MEANS HAVING FREELY ROLLING ELEMENTSAND DISPOSED IN THE SPACE AND HELD IN AXIAL COMPRESSION BETWEEN THESHOULDERS, WHEREBY THE FORCES DEVELOPED BETWEEN THE CONVEYOR AND THEROTOR AS THE CONVEYOR MOVES THE SOLIDS TOWARD THE SOLIDS DISCHARGE PORTAPPEAR AS A COMPRESSIVE FORCE ACTING AT THE INNER JUNCTURE INSTEAD OF ASA TENSION FORCE AT THE OUTER JUNCTION.